Field of the Invention
The present disclosure relates to a resin material for dental milling and machining constituted with a plurality of layers different from each other in transparency and color tone, for preparing dental prosthetic devices (crowns, bridges).
Description of the Related Art
As a dental prosthetic treatment, there has hitherto been adopted a technique to apply to a tooth loss portion a dental crown prepared by casting of an alloy material. This is a prosthetic device preparation technique in which a dental caries portion of a tooth is removed by milling, the negative mold of the remaining tooth is taken with an impression material, plaster is poured into the negative mold to prepare a tooth model, the tooth loss is restored on the tooth model with wax, and the form of the wax is replaced with an alloy by the lost wax method to prepare a prosthetic device.
As a prosthetic device, in addition to an alloy material, a ceramic material or a resin material is sometimes used. When these materials are used, generally adopted is a method in which the prosthetic devices are also prepared by piling each of these materials on the plaster model restoring the lost tooth.
Recently, owing to the development of the dental CAD/CAM technique, the following technique has come to be used: the plaster model reproducing a lost tooth is optically scanned to produce a digital data of the lost tooth on a computer, a digital data of a prosthetic device is produced on the basis of the digital data of the lost tooth, and the prosthetic device is prepared by milling and machining a material on the basis of the digital data of the prosthetic device. For such a preparation of a prosthesis on the basis of the CAD/CAM technique, various materials (such as an alloy, a ceramic, and a resin) are required to be molded beforehand into block bodies (such as a rectangular shape and a disk shape).
With respect to the color tone of a prosthetic device, an alloy material is greatly different in color tone from natural teeth and accordingly aesthetically unsuitable for prosthetic devices. For the preparation of prosthetic devices conforming in color tone to natural teeth and high in aesthetic performance, ceramic materials and resin materials are used. In those conventional methods in which materials are manually piled on plaster models, it is possible to reproduce the same color tone as the color tone of natural teeth by piling ivory-colored materials or enamel-colored materials in layers.
In contrast, in order to prepare prosthetic devices high in aesthetic performance by using materials molded in block shapes for the CAD/CAM technique, it is required to arrange beforehand in the block bodies the same ivory color and the same enamel color as the color of natural teeth.